Any idea what could be causing these issues?

I have a 2.1 GHz Intel Core Duo, 2 GB RAM 17" MBP Running OSX 10.5.8
And I keep experiencing these almost permanent lines across my screen (shown in photo 3) with occasional glitches and other problems show in the rest of the photos. Apple ran its diagnostics test on it 5 times and determined it isnt a hardware issue. If you look at the top right corner you can see the temperature of the computer. I believe this is a over heating issue. I am also experiencing freezing.